Apparatus for false-twisting thermoplastic yarn



Nov. 3, 1964 1.. VAN ASSENDELFT ETAL 3J 5 4,906

APPARATUS FOR FALSE-TWISTING THERMOPLASTIC YRN Fled Nov. 22. 1960 INVENTORS.

LEENDERT VAN ASSENDELFT JAMES WATT IJSBRAND HEIJNIS PIETER KLAAS uoonoeneos HENDRIK wonmsaecusn ATTG? NEY Un1'ted States Patent 3154,906 APPARA'IUS FOR FALSE-TWSTING THERMO- PLASTIC YARN Leendert van Assendelt't and lames W att Ijsbrand, Heijnis, Arnhem, Pieter Klaas Noordenbos, Ede, and Hendrik Wormsbecher, Arnhem, Netheriands, assignors to N.V. Onderzoekingsinstituut Research, Arnhem, Netherlancls, a corporation of the Netherlands Filed Nov. 22, 1960, Set. No. 71,081 Claims priority, appiication Netherlamis Dec. 1, 1959 11 Claims. (Cl. 57-34) This invention relates to the curling of thermoplastic filarnentary materials such as threacls or yarns, and relates more particularly to improvemerrts in the alse-twisting of thermoplastic yarn to rimpart a curl to the yarn.

Curly yarn having a base of thermoplastic material has been prepared by passing the yarn through a falsetwisting device, and heating and cooling the yarn before the twist is taken out. Thus, yarn is fed from a suitable supply package, via a twist barrier, a heating device and a cooling zone, to a false-twisting device, and then to a yarn take-up device. The false-twisting device applies a temporary high twist to the yarn which is substantially completely fixed in the fixation zone. After leaving the false-twisting device, the yarn returns te its condition of low twist or no twist and is characterized by having a permanent tendency to curl and a high degree of elasticity.

As is well known, the degree of curl imparted to the yarn is a function of the twist present in the yarn when the curl is set. Accordingly, it is an important desideratum that as much false-twist be put into the yarn as possible. Moreover, to obtain a strong and uniform curl in the yarn, the false-twisting must be applied uniformly.

Many expedients have been proposed to false-twist yarns uniformly and speedily. One such false-twisting device compn'ses a disc rotatable about its axis with the yarn to be false-twisted adapted to be pressed into engagement with the edge of the disc transversely thereof. In this manner the yarn rolls off over the edge of the disc resulting in a false-twist being placed in the yarn. Another known false-twisting device co-rnprses a ring rotatable in its plane with the yarn to be false-twisted passing through the ring in contact with the inner surface thereof. The yarn guiding means employed with the disc or ring devices causes the yarn to come into contact therewith at one predetermined point. While it is possible to apply a false-twist to yarn with disc or ring false-twisting devices,

such devices have certain disadvantages. Thus, due to the fact that disc -and ringelements are round, they can each false-twist but one, and in exceptional cases tvvo, yarns in a twisting device comprising several twisting units in horizontal alignment.

While it is theoretically possible to provide a twisting device wherein the yarn guiding means delivers a plurality of yarns to the false-twisting device in such an arrangement that the yarns are in a circular alignment With the disc or ring in the center, in which oase one disc 01 ring could simultaneously false-twist several yarns, this assembly is disadvantageous from a structural standpoint.

Another disadvantageous result inherent in the use of dsc or ring false-twisting devices concerns the quality of the false-twisted yarns produced thereby. Thus, where the yarn rides over the edge of a dsc er over the inner surface of a ring, it is found that the false-twst obtained is not constant but fluctuates within certain values. This fluotuation is caused by variations in the point of perpheral contact that the yarn has with the disk or ring. This point contact imparts a twisting component to the travelling yarn. Variations in the location of the yarn contact point on the disk or ring Will result in a van'ation of the velocity of the twisting component. Accordingly, variations in the twisting component cause an irregula:r falsetwist to be irnparted to the yarn. This irregularity of false-tvvist is carried over to the heating zone resulting in an irregular setting of the yarn therein. Obvously, a uniform curling of the yarn cannot be obtained in this marmer.

It is an important object of this invention to overcome the disadvantages of the prior art expedients to produce curled thermoplastic yarns.

Anotl1er object of this invention is to provide an improved app aratus fo-r curling thermoplastic yarn.

Still another object of this inventon is the provision of an improved process for curling thermopiastic yarn.

A further object of this invention is the provision of a uniformly curled thermoplastic yarn.

Other objects and advantages of this invention, together with certain details of construction and combinations of parts of the apparatus, Will appear from the following detailed description.

The alse-twisting device in aceordance With this invention comprises a flexible endless yarn contacting belt which is stretched over deflecting means. The deflecting rneans cooperates With means adapted to drive the endless belt. Many advantages are ganed by the use of the endless belt driven by the means of this invention. For exarnple, the endless belt rnay run the whole length of a tvvisting machine comprising a bank of curling devices and thereby serve as the single false-twisting means for several curling devices, makling for simplieity of construction. Moreover, exceptionally high uniformity of false-twist is obtained in the yarns being processed since the stretched endless belt is constrained to travel along a straight line as it traverses the linear paths of the yarns coming into contact therewith. As a result, the velocity of the belt is transmitted to the yarns at each point of contact. In this marmer, a uniform false twist is obtained in each of the several yarns.

The yarns being false-twisted apply pressure on the endless belt at the point of contact therewith. With all of the yarns of an entire series of curling devices exerting pressure on the endless belt at the sarne time, the endless belt is prone to bend. To permit this bending of the endless belt would be disadvantageous since the condition at each curli-ng device in a series would be different from the conditions existing at the other curling devices, thus resulting in curled yarns which are not uniform. In order to avoid this bending of the endless belt, rollers may be employed to support theendless belt. However, in accordance With this invention. it is preferred to position a plate or rod adjacent the belt and. contacting the belt on the side of the belt opposite to that contacting the yarn whereby when pressure is exerted on the belt by the yarn the belt is precluded trom bending by the support provided by the plate or rod. By the use of the supporting plate identical conditions are obtained at each false-twisting point. Preferably the supporting plate is made of chromium plated or polished steel, or of a suitable synthetic polymeric material, such as a polyamide or polytetrafluoroethylene, in order to decrease the frictional forces developed by the endless belt passing over said supporting plate.

Moreover, to overcome the danger of yarn entanglement or rupture due to strong pull being exerted on the yarn when the false-twisting device is first put into operation, it was found necessary to place yarn guiding means near the endless belt. While it is possible to attach the yarn guiding means individually on the frame of the machine, it is preferred to provide the supporting plate itself with yarn guiding means. T this end the supporting plate may have mounted thereon yarn guidng eyelets or pigtail guides; however, slits or notches formed in the edges of the supporting plate have been found to be very satisfactory yarn guides, while reducing the cost thereof.

The endless belt employed in accordance with this invention may be of any suitable shape. However, while beits of V-shaped or rectangular cross-section may be employed, the most advantageous shape for the endless belt is a circular cross-section where the driving means imparts both a longitudinal movement, and simultaneously, a rotational movement to the endless belt. In fact, endless beits of non-circular cross-section can have uniform travel in a closed path only ifthey are moved accurately and in a longitudinal direction. Where the yarn being false-twisted moves in contact with and across the endless belt in a transverse direction, the yarn will be false twisted with a simultaneous increase in tension. This increase in tension occurs since the yarn must be pulled over the endless belt in a slipping manner to overcome frictional resistance. This increase in tension is olten undesirable. Moreover, the transmission of the false-twisting movement to the yarn by the endless belt is unfavorably influenced due to the slippage. These disadvantages may be avoided by rotating the endless belt transversely, as well as longitudinally, and adjusting the transverse rotational velocity of the endless belt to be equal to the velocity of the yarn travel ing over the belt.

An endless belt with a circular cross-section has the advantage that it may simply be rotated along its longitudinal direction in a closed path without the travel of the endless belt becoming irregular. The contact of the yarn with an endless belt of circular cross-section is, moreover, simlar in any position of the endless belt, so that an undisturbed running of the yarn is obtained.

The driving of such an endless belt simultaneously in and around its longitudinal direction makes special demands on the driving means. According to this inven tion, a simple solution to the problem consists in the use of a driving means comprising a pair of hyberboloid rollers the axes of which cross each other at an angle twice the magnitude of the crossing angle between the generatrices of the hyperboloid rollers and their axes. Such a pair of hyperboloids is described in Patent No. 2943,433 to Van Dijk for the false-twisting of a yarn. It has now been found that said hyperboloids may be used with success to give an endless belt the above described movement.

The driving of the endless belt in the above described marmer requires means for guiding or deflecting the endless belt around the hyperboloid driving means. Where the endless belt is moved in a longitudinal direction only, smple rollers which are freely rotatable about their axes, with the axes of said rollers in the plane of the endless belt, make satisfactory deflecting means. However, where it is required that the endless belt be rotated about its longitudinal direction difiicultes arise such as, for exarnple, the danger that the endless belt will roll o the deflecting rollers. According to this invention, there is provided a simple and satisfactory means for deflecting the endless belt in its course of travel. Thus, the de flecting means of the endless belt comprises freely rotatable rollers the axes of which are so placed in an inclined position in the plane of the endless belt trained over said rollers that said endless belt runs in a hclical line. Surprisingly, it is found that there is. always a position of the deflecting rollers in which the endless belt remains satisfactorily in place on the rollers. The thickness of the rollers is not very critical. According to the invention, this thickness is preferably in the order of 5 to about Besdes the alse-twisting device described, the apparatus for curling of thermoplastic yarns, in accordance with this invention, comprises a yarn supply device, a twist barrier, a heating device, a cooling zone, and a yarn discharge device. As indicated above, it is of advantage to place the yarn guidng means close to the endless belt in order to prevent dragging the yarn along with the endless belt in its longitudinal direction of travel. It has, however, been found that the yarn should contact said guiding means as little as possible in order to pre vent darnage to the yarn and irregularities in the falsetwist. According to this invention contact between the yarn and the guiding means may practically completely be avoided if the heating device is placed at an acute angle to the direction of travel of the endless belt. In this marmer there is exerted on the yarn a force which retains the yarn in a direction opposed to the direction of travel of the endless belt.

By a suitable adjustment of the angle of: the heating device, an equilibrium may be established between said action of orce and the dragging action on the yarn by the endless belt.

In the accompanying drawing which illustrates one of a plurality of sirnilar curling units arranged in a bank,

FIGURE 1 is a diagrarnmatic view in front elevation of a continuous curling unit constructed in accordance with a preferred embodiment of this invention,

FIGURE 2 is a side elevational view of the curling unit shown in FIGURE 1, and

FIGURE 3 is a detail view, on a slightly enlarged scale, of the endless belt driving and deflectng means arranged in the path of the endless belt.

Referring now to FIGURES 1 and 2, the reference numeral 1 indcates a yarn supply package containing uncurled yarn having a base of a synthetic polymeric material, and the reference numeral 2 indicates a yarn take-up package. The uncurled yarn 3 from the supply package 2 is drawn therefrorn through a guide eye 4 suitably held above package 1, is passed through the means for curlng the same hereinafter set forth, and is taken up in curled, elastic form on package 2.

The yarn package 1 is carried on a stationary support 5 and is fixed thereon in any convenient manner. The support 5 runs the full length of the machine and is adapted to carry a supply package for each of the curling units of the machine.

The yarn take-up package 2 is positioned on a twisting spindle 6 arranged on a beam 7 which also runs the ful length of the machine and on which a twisting spindle is provided for each curling unit. The twisting spindle is driven by a belt 8 and the yarn package 2 is built up in the conventional manner by a traveller ring and reciprocating ring rail 9, respectively.

The yarn 3 is passed trom guide eye 4 between cooperating rollers 10 and 11, the roller 10 being driven by shaft 12 and the roller 11 being an idler roller which may be provided with means (not shown) for applying pressure on the roller 10. A second set of rollers similar to rollers 10 and 11 are positioned below the false-twisting means, to be described, to discharge the yarn therefrom. These rollers are indicated by reference numerals 13 and 14 with the former being driven by a shaft 15.

The elements described above are norrnally used in curling devices and may be replaced by other smilarly functioning elements, or may be arranged diterently so long as their functions remain the same.

The novel features of this invention will now be described.

The yarn 3, after leaving the rollers 10 and 11, passes through a heating tube 16 which is arranged in en inclined position as shown in FIGURES 1 and 2. From the heating tube the yarn passes tbrough the air where it is cooled. In this cooling air zone the yarn is fixed in twisted form, the twisting being etected by means described below. After leaving the cooling airzone to pass between rollers 13 and 14, the yarn is adapted to come into contact with a substantial portion of the periphery of an endless belt 17 of circular cross-section, the endless belt being preferably made of rubber, al though endless belts of other suitable materials may be employed. A belt having a diameter of mm. has been found to be satisfactory.

In front of endless belt 17 there is positioned a plate 18, preferably arcuate in form, which is provided with notches 19 for receiving and guiding the yarn. The endless belt, only a portion of which is shown in the drawing, travels trom right to left as indicated by the arrows.

The inclination of the heating tube 16 is such that contact of the yarn to be twisted with the guide notches 19 is substantially avoided thereby preventing damage to the yarn and substantially eliminating the danger of rregularly twisting yarn. Frictional contact with guide notches 19 would tend to act in a twist limiting manner and prevent the eect of the twist trom reaching the heating zone. A varying frictional contact would produce an irregularly false twisted yarn. Yarn contact with the notches 19 would also tend to cause breakage of the filaments and the production of knops, slubs and projecting filament ends on the traveling yarn.

ln FIGURE 3 there is shown the means for drivng the endless belt 17 and the delecting means cooperating with the driving means. Thus, the deflectng means, rollers 20 and 21, are arranged in a horizontal plane, freely rotatable about tl1eir axes and inclined in such a marmer that the belt passes helically thereover. The driving means for the endless belt 17 comprises a pair of driven hyperboloid rollers 22 and 23 which are po sitioned between the rollers 20 and 21 in such a manner that the belt passes between and in contact with the hyperboloid rollers. Any suitable means (not shown) may be employed for driving the hyperboloid rollers in the drections indicated by the arrows.

The hyperboloid rollers 22 and 23 are so mounted in operative position that their axes cross each other at an angle twice the magnitude of the crossing angle between the generatrices of the hyperboloid rollers and their axes. In accordance with the arrangement of the hyperboloid rollers relative to each other, the belt 17 contacts the same either according to straight generatrices of the hyperboloicls or at points where the belt is perpendicular to the generatrices through sad points.

Means (not shown) may be employed to press the hyperboloid rollers toward each other to come into contact with the belt passing therebetween, and by driving the sad rollers in the directions indicated by the arrows, the belt will be driven in the desired marmer.

While theoretically the yarn can be false-twisted to a centain degree with a particular arrangement of hyperboloid rollers 22 and 23 with the deilecting rollers 20 and 21 in particular position, it was found in actual practice that a range of false-twisting, a range amply sufiicient for all practical purposes, can be realized with the combination described herein. It will be appreciatecl that the degree of false-twisting depencls upon the denier of the yarn being false-twisted.

It is to be understood that the oregoing detailed description is given merely by way of illustration and that many variations may be made therein without departiiig from the spirit of this invention.

What is claimed is:

1. in an apparatus for imparting a curl to yarn, a falsetwisting device comprising a flexible endless belt, means for driving sad endless belt, and means for guiding the yarn to be false-twisted into contact with sad endless belt,

a portion of sad yarn guiding means defining a surface, which surface is positioned adjacent sad endless belt on the side of sad belt opposite to that which is contacting sad yarn so that sad belt is precluded trom bending under pressure exerted on sad belt -by sad yarn.

2. Apparatus according toclaim 1 wherein the yarn guiding means includes-a plate extending over a portion of the path of travel of the endless belt, sad plate having guiding no-tches therein and an inclined heating tube through which the yarn is =adapted to pass towa-rds the endless belt.

3. Apparatus according to claim 2 wherein the hcating tube is positioned above the endless belt at an acute angle to the direction of travel thereof.

4. An apparatus for imparting a curl to yarn comprising a fialse-twistng device comprising a flexible endless belt having a circular cross-section, means for driving sad endless belt so that sad belt throughout its path of tr-avel is caused to have simultaneously a longitudinal movement in the direction of travel thereof and a rotating movement about the direction of travel thereof, and means f-or guiding the yarn to be false-twisted into contact with sad endless belt.

5. The apparatus according to claim 4 wherein sad endless belt is made of rubber and has a diameter of trom about 5 to about 10 mm.

6. The apparatus according to claim 4 wherein a portion of sad yarn guiding means defines a surface, which surface is positioned adjacent sad endless belt on the side of sad belt opposite to that which is contacting sad yarn so that sad belt is precludecl trom bending under pressure exerted on sad belt by sad yarn.

7. An apparatus for imparting a curl to yarn comprising a false-twisting device comprising a flexible endless belt having a circular cross-section, means for driving sad endless belt comprising a pair of hyperboloid rollers whereby the belt is caused to have simultaneously a longitudinal movement in the direction of travel thereof and a rot-atng movernent about the direction of travel thereof, and means for guiding the yarn to be falsetwisted into contact with sad endless belt.

8. The apparatus according to claim 7 wherein sad endless belt is made of rubber and has a diameter of trom about 5 to about 10 mm.

9. The apparatus according to claim 7 wherein a portion of sad guiding means defines a surface, which surface is positioned adjacent sad endless belt on the side of sad belt opposite to that which is contacting sad yarn so that sad belt is precluded trom bending under pressure exerted on sad belt by sad yarn.

10. The apparatus according to claim 7 wherein the axes of the pair of hyperboloid rollers cross each other at an angle twice the magnitude of the crossing angle between the generatrices of the hyperboloid rollers and the axes thereof.

11. The apparatus acocrding to claim 7 wherein the endless belt is stretcl1ed over deflecting means arranged in the patl1 of the endless belt and the deflecting means comprises freely rotatable rollers, the =axes of sad rollers being inclined to the plane of the endless belt whereby the belt travels over the rollers helically.

References Cited in the file of this patent UNITED STATES PATENTS 151,256 Walker May 26, 1874 1,032268 Bense July 9, 1912 1075,184 Beede Oct. 7, 1913 2101,172 Gegenheimer Dec. 7, 1937 2590,374 Brown Mar. 25, 1952 2601,394 Hansen June 24, 1952 2890,568 Willems Iune 16, 1959 (ther references on following page) UNITED STATES PATENTS 8 FOREIGN PATENTS Belgum Nov. 30, 1953 Germany Mar. 8, 1954 Great Brtan Apr. 10, 1957 G'at Britan Sept. 17, 1958 OTI-IER REFERENCES 507 Mechancal Movements, by Henry T. Brown, Brown and Seward Publishers, Twenteth Edition. Copy- Vandamme et al June 23, 1959 524,008 St0ddard et al Iune 23, 1959 905,826 Brown Oct. 13, 1959 772,346 Cecchi Dec. 15, 1959 801,464 Arthur et al. May 17, 1960 Van Dijk July 5, 1960 Schrenk et al. Aug. 23, 1960 Gonsalves et al Sept. 20, 1960 Comer et al Jan. 24, 1961 19 gh 1863 

1. IN AN APPARATUS FOR IMPARTING A CURL TO YARN, A FALSETWISTING DEVICE COMPRISING A FLEXIBLE ENDLESS BELT, MEANS FOR DRIVING SAID ENDLESS BELT, AND MEANS FOR GUIDING THE YARN TO BE FALSE-TWISTED INTO CONTACT WITH SAID ENDLESS BELT, A PORTION OF SAID YARN GUIDING MEANS DEFINING A SURFACE, WHICH SURFACE IS POSITIONED ADJACENT SAID ENDLESS BELT ON THE SIDE OF SAID BELT OPPOSITE TO THAT WHICH IS CONTACTING SAID YARN SO THAT SAID BELT IS PRECLUDED FROM BENDING UNDER PRESSURE EXERTED ON SAID BELT BY SAID YARN. 